Gas turbine engines typically include a fan delivering air into a bypass duct defined within a nacelle, and also into an engine core. The air in the engine core passes through a compressor section, and then into a combustion section. In the combustion section the air is mixed with fuel and ignited, and products of this combustion pass downstream over turbine rotors.
The formation of ice on aircraft structures, for example engine inlets, wings, control surfaces, propellers, booster inlet vanes, inlet frames, etc., is a problem for contemporary aircraft. Ice adds weight, increases drag, and alters the aerodynamic contour of airfoils, control surfaces and inlets, all of which reduce performance and consequently increase the fuel consumption of a gas turbine engine. In addition, ice permitted to form on aircraft structures can become dislodged and impact other aircraft parts and engine components, causing damage.
Contemporary aircraft can include systems that take hot air from the engines of the aircraft for use within the aircraft; for example, a nacelle anti-icing system can use hot air from the engines to heat portions of the nacelle inlet. The nacelle anti-icing system typically will tap hot air from the compressor section and selectively deliver it to the inlet of the nacelle to provide anti-icing at the lip of the nacelle. This anti-icing function is performed selectively and when conditions indicate that there can be icing at the lip of the nacelle, the valve can be opened to deliver the hot air to that location.